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<h1 id="sec_name">
<span data-if="hdevelop" style="display:inline;">fread_line</span><span data-if="c" style="display:none;">T_fread_line</span><span data-if="cpp" style="display:none;">FreadLine</span><span data-if="dotnet" style="display:none;">FreadLine</span><span data-if="python" style="display:none;">fread_line</span> (算子名称)</h1>
<h2>名称</h2>
<p><code><span data-if="hdevelop" style="display:inline;">fread_line</span><span data-if="c" style="display:none;">T_fread_line</span><span data-if="cpp" style="display:none;">FreadLine</span><span data-if="dotnet" style="display:none;">FreadLine</span><span data-if="python" style="display:none;">fread_line</span></code> — Read a character line from a text file.</p>
<h2 id="sec_synopsis">参数签名</h2>
<div data-if="hdevelop" style="display:inline;">
<p>
<code><b>fread_line</b>( :  : <a href="#FileHandle"><i>FileHandle</i></a> : <a href="#OutLine"><i>OutLine</i></a>, <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
</div>
<div data-if="c" style="display:none;">
<p>
<code>Herror <b>T_fread_line</b>(const Htuple <a href="#FileHandle"><i>FileHandle</i></a>, Htuple* <a href="#OutLine"><i>OutLine</i></a>, Htuple* <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
</div>
<div data-if="cpp" style="display:none;">
<p>
<code>void <b>FreadLine</b>(const HTuple&amp; <a href="#FileHandle"><i>FileHandle</i></a>, HTuple* <a href="#OutLine"><i>OutLine</i></a>, HTuple* <a href="#IsEOF"><i>IsEOF</i></a>)</code></p>
<p>
<code>HString <a href="HFile.html">HFile</a>::<b>FreadLine</b>(Hlong* <a href="#IsEOF"><i>IsEOF</i></a>) const</code></p>
</div>
<div data-if="com" style="display:none;"></div>
<div data-if="dotnet" style="display:none;">
<p>
<code>static void <a href="HOperatorSet.html">HOperatorSet</a>.<b>FreadLine</b>(<a href="HTuple.html">HTuple</a> <a href="#FileHandle"><i>fileHandle</i></a>, out <a href="HTuple.html">HTuple</a> <a href="#OutLine"><i>outLine</i></a>, out <a href="HTuple.html">HTuple</a> <a href="#IsEOF"><i>isEOF</i></a>)</code></p>
<p>
<code>string <a href="HFile.html">HFile</a>.<b>FreadLine</b>(out int <a href="#IsEOF"><i>isEOF</i></a>)</code></p>
</div>
<div data-if="python" style="display:none;">
<p>
<code>def <b>fread_line</b>(<a href="#FileHandle"><i>file_handle</i></a>: HHandle) -&gt; Tuple[str, int]</code></p>
</div>
<h2 id="sec_description">描述</h2>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></code> reads a whole line (including the line break
character) from the input file defined by the handle <a href="#FileHandle"><i><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></i></a>.
The input file must have been opened with <a href="open_file.html"><code><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></code></a> in text format.
</p>
<p>The read line is returned in parameter <a href="#OutLine"><i><code><span data-if="hdevelop" style="display:inline">OutLine</span><span data-if="c" style="display:none">OutLine</span><span data-if="cpp" style="display:none">OutLine</span><span data-if="com" style="display:none">OutLine</span><span data-if="dotnet" style="display:none">outLine</span><span data-if="python" style="display:none">out_line</span></code></i></a>.
It starts at the current file position and ends at the end of the file or
with the first line break character found.
A subsequent read operation on the file would start after the line break,
i.e., at the beginning of the next line.
If needed, the output string is transcoded into the current encoding of the
HALCON library (the default is UTF-8).
</p>
<p>The range of control characters that are handled as line break depends on
the file encoding, which can be specified when the file is opened with
<a href="open_file.html"><code><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></code></a>.
The standard line break characters are
<i><span data-if="hdevelop" style="display:inline">'\n'</span><span data-if="c" style="display:none">"\n"</span><span data-if="cpp" style="display:none">"\n"</span><span data-if="com" style="display:none">"\n"</span><span data-if="dotnet" style="display:none">"\n"</span><span data-if="python" style="display:none">"\n"</span></i> (line feed),
<i><span data-if="hdevelop" style="display:inline">'\r'</span><span data-if="c" style="display:none">"\r"</span><span data-if="cpp" style="display:none">"\r"</span><span data-if="com" style="display:none">"\r"</span><span data-if="dotnet" style="display:none">"\r"</span><span data-if="python" style="display:none">"\r"</span></i> (carriage return), and
<i><span data-if="hdevelop" style="display:inline">'\f'</span><span data-if="c" style="display:none">"\f"</span><span data-if="cpp" style="display:none">"\f"</span><span data-if="com" style="display:none">"\f"</span><span data-if="dotnet" style="display:none">"\f"</span><span data-if="python" style="display:none">"\f"</span></i> (form feed).
These characters are accepted on all encodings or when the encoding has to
be ignored.
The line break sequence
<i><span data-if="hdevelop" style="display:inline">'\r\n'</span><span data-if="c" style="display:none">"\r\n"</span><span data-if="cpp" style="display:none">"\r\n"</span><span data-if="com" style="display:none">"\r\n"</span><span data-if="dotnet" style="display:none">"\r\n"</span><span data-if="python" style="display:none">"\r\n"</span></i>
(carriage return + line feed), which
is the default line break under Windows, is handled (on all systems)
as one line break and returned as
<i><span data-if="hdevelop" style="display:inline">'\n'</span><span data-if="c" style="display:none">"\n"</span><span data-if="cpp" style="display:none">"\n"</span><span data-if="com" style="display:none">"\n"</span><span data-if="dotnet" style="display:none">"\n"</span><span data-if="python" style="display:none">"\n"</span></i> in the output string.
In UTF-8 encoded files, the following Unicode control code points will also
terminate the read line: <i><span data-if="hdevelop" style="display:inline">'U+0085'</span><span data-if="c" style="display:none">"U+0085"</span><span data-if="cpp" style="display:none">"U+0085"</span><span data-if="com" style="display:none">"U+0085"</span><span data-if="dotnet" style="display:none">"U+0085"</span><span data-if="python" style="display:none">"U+0085"</span></i> (next line), <i><span data-if="hdevelop" style="display:inline">'U+2028'</span><span data-if="c" style="display:none">"U+2028"</span><span data-if="cpp" style="display:none">"U+2028"</span><span data-if="com" style="display:none">"U+2028"</span><span data-if="dotnet" style="display:none">"U+2028"</span><span data-if="python" style="display:none">"U+2028"</span></i>
(line separator), and <i><span data-if="hdevelop" style="display:inline">'U+2029'</span><span data-if="c" style="display:none">"U+2029"</span><span data-if="cpp" style="display:none">"U+2029"</span><span data-if="com" style="display:none">"U+2029"</span><span data-if="dotnet" style="display:none">"U+2029"</span><span data-if="python" style="display:none">"U+2029"</span></i> (paragraph separator).
</p>
<p>If the end of the file is reached before any character was written to the
output string, the parameter <a href="#IsEOF"><i><code><span data-if="hdevelop" style="display:inline">IsEOF</span><span data-if="c" style="display:none">IsEOF</span><span data-if="cpp" style="display:none">IsEOF</span><span data-if="com" style="display:none">IsEOF</span><span data-if="dotnet" style="display:none">isEOF</span><span data-if="python" style="display:none">is_eof</span></code></i></a> 返回值 <i>1</i>,
otherwise <i>0</i>.
</p>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></code> emits a low-level error message, when
it encounters bytes that do not represent a valid code point in the
specified encoding.
Despite of the low-level error message, 该算子 will not fail and
<a href="#OutLine"><i><code><span data-if="hdevelop" style="display:inline">OutLine</span><span data-if="c" style="display:none">OutLine</span><span data-if="cpp" style="display:none">OutLine</span><span data-if="com" style="display:none">OutLine</span><span data-if="dotnet" style="display:none">outLine</span><span data-if="python" style="display:none">out_line</span></code></i></a> will contain potentially invalid bytes
(invalid within the specified encoding).
Furthermore, 该算子 also emits a low-level error message, when the
output string cannot be transcoded without loss of information into the
current encoding of the HALCON library.
For a correctly encoded string this can only happen when the file is
UTF-8 encoded and the current encoding of the HALCON library is
<i><span data-if="hdevelop" style="display:inline">'locale'</span><span data-if="c" style="display:none">"locale"</span><span data-if="cpp" style="display:none">"locale"</span><span data-if="com" style="display:none">"locale"</span><span data-if="dotnet" style="display:none">"locale"</span><span data-if="python" style="display:none">"locale"</span></i> (see <a href="set_system.html"><code><span data-if="hdevelop" style="display:inline">set_system(::'filename_encoding','locale':)</span><span data-if="c" style="display:none">set_system("filename_encoding","locale")</span><span data-if="cpp" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="com" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="dotnet" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="python" style="display:none">set_system("filename_encoding","locale")</span></code></a>).
</p>
<h2 id="sec_execution">运行信息</h2>
<ul>
  <li>多线程类型:可重入(与非独占操作符并行运行)。</li>
<li>多线程作用域:全局(可以从任何线程调用)。</li>
  <li>未经并行化处理。</li>
</ul>
<h2 id="sec_parameters">参数表</h2>
  <div class="par">
<div class="parhead">
<span id="FileHandle" class="parname"><b><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></b> (input_control)  </span><span>file <code>→</code> <span data-if="dotnet" style="display:none"><a href="HFile.html">HFile</a>, </span><span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">HHandle</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (handle)</span><span data-if="dotnet" style="display:none"> (<i>IntPtr</i>)</span><span data-if="cpp" style="display:none"> (<i>HHandle</i>)</span><span data-if="c" style="display:none"> (<i>handle</i>)</span></span>
</div>
<p class="pardesc">File handle.</p>
</div>
  <div class="par">
<div class="parhead">
<span id="OutLine" class="parname"><b><code><span data-if="hdevelop" style="display:inline">OutLine</span><span data-if="c" style="display:none">OutLine</span><span data-if="cpp" style="display:none">OutLine</span><span data-if="com" style="display:none">OutLine</span><span data-if="dotnet" style="display:none">outLine</span><span data-if="python" style="display:none">out_line</span></code></b> (output_control)  </span><span>string <code>→</code> <span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">str</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (string)</span><span data-if="dotnet" style="display:none"> (<i>string</i>)</span><span data-if="cpp" style="display:none"> (<i>HString</i>)</span><span data-if="c" style="display:none"> (<i>char*</i>)</span></span>
</div>
<p class="pardesc">Read line.</p>
</div>
  <div class="par">
<div class="parhead">
<span id="IsEOF" class="parname"><b><code><span data-if="hdevelop" style="display:inline">IsEOF</span><span data-if="c" style="display:none">IsEOF</span><span data-if="cpp" style="display:none">IsEOF</span><span data-if="com" style="display:none">IsEOF</span><span data-if="dotnet" style="display:none">isEOF</span><span data-if="python" style="display:none">is_eof</span></code></b> (output_control)  </span><span>integer <code>→</code> <span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">int</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (integer)</span><span data-if="dotnet" style="display:none"> (<i>int</i> / </span><span data-if="dotnet" style="display:none">long)</span><span data-if="cpp" style="display:none"> (<i>Hlong</i>)</span><span data-if="c" style="display:none"> (<i>Hlong</i>)</span></span>
</div>
<p class="pardesc">Reached end of file before any character was read.</p>
</div>
<h2 id="sec_example_all">例程 (C)</h2>
<pre class="example">
do {
  fread_line(FileHandle,&amp;Line,&amp;IsEOF);
} while(IsEOF==0);
</pre>
<h2 id="sec_result">结果</h2>
<p>If the file is open and a suitable line is read, <code><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></code>
返回值 <TT>2</TT> (
      <TT>H_MSG_TRUE</TT>)
    .
Otherwise, an exception is raised.
Encoding errors have no influence on the result state.
</p>
<h2 id="sec_predecessors">可能的前置算子</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>
</p>
<h2 id="sec_successors">可能的后置算子</h2>
<p>
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>
</p>
<h2 id="sec_alternatives">可替代算子</h2>
<p>
<code><a href="fread_char.html"><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></a></code>, 
<code><a href="fread_string.html"><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></a></code>
</p>
<h2 id="sec_see">参考其它</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>, 
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>, 
<code><a href="fread_char.html"><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></a></code>, 
<code><a href="fread_string.html"><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></a></code>
</p>
<h2 id="sec_module">模块</h2>
<p>
Foundation</p>
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